328 The American Ueoloiiist. Niwcmbpr, 1*96 
sylvania. The Clinton, on the other hand, is an important factor in 
the state inasmuch as it contains a large amount of iron ore. 
The Lower Helderberg, Formation No. VI, while only a few hundred 
feet thick is interesting from its fossil remains. "A crisis in the PaUe- 
ozoic history is approaching. The sea is shallowing. Living creatures 
are Vjecoming more and more abundant. The smaller shells which lived 
liefore are replaced l)y, or have developed into larger shells: and among 
the trilobites appear articulated animals rivalling in size our modern 
lobsters. A world of coral-like animals flourish in extensive reefs: and 
the bed of the ocean becomes a floor of sponges. It is the age of Strom- 
atopora and Euryptervis. Suddenly this wonderful exhibition comes to 
an end. An invasion of sharp sand gi-ains with a proportion of clay and 
a tincture of lime, Formation No. VII [Oriskany of New York], invades 
the ocean and covers up the dead Ijody of its animal life. Almost a new 
order of nature is inauguratetl; new species and genera of animals ap- 
pear: the great bucklered fish take possession of the sea; trilobites 
change their character and live in diminished numbers; black mud is 
poured from the rivers and settles upon the ocean bed: the first intima- 
tion of the creation of coal is given for a moment and then withdrawn; 
the great water basin deepens; and ten thousand feet of sandy and 
muddy deposits fill it up again; until, finally, the age of the true Coal 
Measures sets in and the Palreozoic record of the world is made com- 
plete" (pp. 898-899). 
A graphic pict\u-e truly of geological change in the Lower Helderberg 
age. The variations in deposits, the great profusion of organic forms, 
and its wide distribution are all commented upon. The wonderful 
Stromatopora reef or bed is also discussed. 
The Oriskany sandstone {Areskana is considered the correct name, 
p. 1034) is considered to mark the boundary between Palaeozoic and De- 
vonian strata. The Cauda-galli grit is regarded as probably the top 
member of the Oriskany rather than the basal member of the Upper 
Helderberg. This last is divided into seven beds, Corniferous, Marcel- 
lus, Hamilton, Tully, Genesee, Portage and Chemung, in ascending 
order, and each one is descriV)ed in detail. Some interesting remarks on 
Spirifeva are found on pages 1391-1395. In the Chemung occurs the 
Venango oil sand and this is described in great detail. 
Prof. Lesley's work in this Final Summary closes at page 18.')3 in vol- 
ume 3, and the remaining pages, devoted to the anthracite and bitumin- 
ous coal fields, are by other hands. Mr. E. V. d'Invilliers describes the 
Mauch Chunk red shale, Pottsville conglomerate and the bituminous 
coal districts, while Mr. A. D. W. Smith untertakes the anthracite coal 
districts. The latter is considered first and the wonderful growth of 
the industry is manifest when it is noted that from 1840, when the an- 
nual product was about one million tons, it had increased in 1880 to 
25,000,000 tons, and in 1893 to 48.185,306 tons. This was valued at S85,- 
687,078 and the vast amount was taken from an area of 484 square miles. 
It was exceeded only by the output of bituminous coal, valued at $122,- 
751,618, produced by mines covering an area of 200,000 square miles. 
